Follow your curiosity

What discovery has been shared with you?

FACTREE gives you something interesting to discover every day — and something worth talking about together.

Start with one fact. Explore it, go deeper, then follow whichever branch catches your imagination.

Choose subjects for a surprise

Exploring any topic

Begin your discovery

Your next discovery is one click away.

Choose one or more subjects above, or leave Any Topic selected and let curiosity decide.

Chemistry

Why Octopuses Have Three Hearts: The Oxygen Connection

Quick fact

Octopus blood is blue because it uses copper-based hemocyanin instead of iron-based hemoglobin to carry oxygen.

Why this is interesting

You know octopuses are incredibly intelligent, but did you know they have three hearts? Why would any creature need that many?